Lake Michigan water levels have staged a big comeback, rising more than 4 feet since early in 2013 when they dropped to an all-time low.

The increase is due to a combination of factors — more rainfall and runoff, and weather conditions that have slowed evaporation from the surface of the lake.

Lake Michigan and Lake Huron are now 2 inches higher than a month ago; 9 inches higher than the same time a year ago, and 13 inches above the long-term average of May, according to the U.S. Army Corps of Engineers. Michigan and Huron are considered a single lake, linked by the Straits of Mackinac.

With seasonal conditions filling rivers and streams, the Lake Michigan system is projected to rise another 2 inches in the next month and will likely add a few more inches this summer, according to the corps.

The situation this spring:

Beaches up and down the shoreline have shrunk. Scientists expect benefits for coastal wetlands. Still, if levels rise too high, newly created spawning grounds might be less hospitable for fish. The need to dredge ports and marinas has declined. And deeper water has allowed commercial shippers to carry more cargo.

For Milwaukee, one outcome could be less odor from the foul-smelling shoreline algae, Cladophora, which rots at the water's edge.

Fewer bird deaths from Avian botulism are also possible, said scientist Harvey Bootsma of the University of Wisconsin-Milwaukee. The botulism is produced when lake conditions are just so, with plenty of dead plant matter and reduced oxygen in the water.

"We have evidence that both of these problems tend to be worse in years when the lake levels are low, and not so bad when the lake levels are high," said Bootsma, who has looked for clues into the deaths of thousands of birds at Sleeping Bear Dunes National Lakeshore in Michigan and other locations.

"There seems to be a pattern there, but we are not sure why."

In hydrological terms, Lake Michigan has risen from 576.02 feet in January 2013 to 580.09 feet today. The lake is still more than 2 feet below its all-time high of 582.35 in October 1986.

As water levels inch up, so have concerns about the erosion of beaches and bluffs.

State Department of Administration spokeswoman Laurel Patrick said in a statement that "bluff erosion is certainly on (the) radar" of the agency's coastal management officials, adding that they are "closely monitoring Lake Michigan's lake levels."

In Milwaukee, property just north of Bradford Beach has caved into the water recently — a situation that a spokeswoman for County Executive Chris Abele says is also being monitored.

In northern Ozaukee County, residents are calling authorities about permit requirements to engineer the placement of rocks along the shoreline to protect disappearing beaches. The number of calls so far has been small, said Andy Holschbach, the county's director of land and water management.

"That could change after this season," Holschbach said. "I am sure the calls are going to increase."

Lakefront residents near Concordia University Wisconsin in Mequon have experienced erosion problems since water levels started rising in 2013.

Vance Strother lost his beach in 2014. By January 2015, wave action and high water had devoured large sections of the bluff.

Many property owners south of the college have blamed the school's massive bluff protection project — a charge the school has denied. Still, Strother said an engineer hired by property owners has estimated that lake erosion has migrated an additional 1,000 feet to the south.

"I think that more people are going to be upset when they see they are losing the toe of their beach," Strother said.

Weather conditions largely dictate the ebb and flow of Lake Michigan water levels.

The springs of 2013, 2014 and 2015 were all wetter than normal, as is this spring, according to Andrew D. Gronewold, a hydrologist with the National Oceanic and Atmospheric Administration.

Other factors: A complex relationship between the extent of ice cover, air temperature and evaporation — especially in the fall, when cold, dry air settles over the relatively warmer temperatures of the lake.

"When you stack all of those years together, you get this pretty interesting jump in water levels going back to January 2013," Gronewold said.

The situation today is a far cry from when the lake plunged to its lowest level since modern records started being kept in 1918.

"I'm working seven days a week trying to get caught up here, and I'll never get to everyone that needs to be taken care of. Winter's closing in, and it's not good."

When contacted last week, Kahr painted a different picture.

"We're doing less dredging, that's for sure," he said.

Now Kahr said he is getting calls asking to assess the impact of rising water levels. Some property owners are asking about having their docks raised.

When Lake Michigan and Lake Huron were at their historic low, some attributed part of the problem to 1960s-era dredging for navigation on Lake St. Clair, which acted to lower lake levels. The lake borders Michigan and Ontario and is the main outlet for the two lakes.

The corps in 2014 allocated $50,000 to study whether water levels could rise with the installation of structures on Lake St. Clair to slow water flows.

The International Joint Commission, which oversees U.S. and Canadian boundary water issues, said it supported an investigation of options that would restore water levels by 5 to 10 inches, according to documents. Knowing that lake levels have historically fluctuated, and could rise again, the commission encouraged the U.S. and Canadian governments to study options for structures that would not cause problems when water levels were higher.

But a potential project on Lake St. Clair is no longer being studied, a corps official said last week.

"There was a general lack of support from the (U.S.) State Department and other agencies," said John Allis, chairman of the Detroit district of the corps.

About Lee Bergquist

Lee Bergquist covers environmental issues and is author of "Second Wind: The Rise of the Ageless Athlete."